Radiation therapy in acromegaly

Abstract

Radiation therapy is generally not a primary treatment modality for growth hormone-secreting pituitary adenomas. However, in patients with acromegaly refractory to medical and/or surgical interventions, radiation can offer durable tumor control and often biochemical remission. Technique of radiation therapy delivery and dose vary by adenoma size and extrasellar extension. Radiation can be delivered in a single sitting by stereotactic radiosurgery or in fractionated form of smaller doses delivered over typically 5-6 weeks in 25-30 treatments. A brief overview of forms of radiation modalities is reviewed followed by discussion of the role for radiation therapy, rationale of delivery method, and potential adverse effects.

Fractionated stereotactic radiotherapy in patients with acromegaly: an interim single-centre audit

“…Comparison between patients treated with FSRT and SRS is complicated since allocation to the different stereotactic treatment modalities is different based on tumour size, shape and location (6,7,30,31). By combining the high radiation precision known from SRS and the radiobiological advantages of fractionated radiation, FSRT is preferred over SRS when the target is close to a critical structure as, for example, the optic pathway (13,32).…”

“…By combining the high radiation precision known from SRS and the radiobiological advantages of fractionated radiation, FSRT is preferred over SRS when the target is close to a critical structure as, for example, the optic pathway (13,32). Also, FSRT is performed mostly using a dental or head mask, thereby avoiding the invasive pins used during SRS (the Cyberknife is an exception) (6). However, SRS is more convenient for patients than FSRT, requiring 1 day versus 6 weeks of treatment (33).…”

“…Most series regarding FSRT to acromegalic patients have a follow-up time shorter than those for SRS (13-17, 20, 30, 32, 34-37) (Tables 5 and 6), which complicates the comparison since the effect of FSRT is known to appear later than the effect of SRS (6). However, the biochemical remission after SRS seems to vary between 21 and 67% (follow-up median 66 months, range 25-114) compared with 0 and 55% after FSRT (follow-up median 42 months, range 28.5-59.8) (13-17, 20, 30, 32, 34-37) (Tables 5 and 6), but the criteria for biochemical remission in both the SRS and FSRT series were not identical.…”

“…Stereotactic techniques have improved RT of acromegaly -mainly due to the high accuracy in the radiation delivery (6). Only stereotactic radiosurgery (SRS) has documented faster hormonal effect than conventional RT (3), but overall SRS and fractionated stereotactic RT (FSRT) result in the same local control (6).…”

“…Only stereotactic radiosurgery (SRS) has documented faster hormonal effect than conventional RT (3), but overall SRS and fractionated stereotactic RT (FSRT) result in the same local control (6). FSRT, though, is recommended when the tumour is close to critical structures (6,7).…”